The problem with a self declared approach is that puts a signalling mechanism in place. Once in place the laws can easily scope creep year over year to add more information or require putting in ID information or some future nation-wide digital ID and Trump coin digital wallet which could easily be the plan all along. All they need is the API that will interface with websites using some agreed upon standard and then it can easily be extended line by line. Give them an inch, they will take a mile.
replyWith proper parental controls there is no signalling.
Ensure system does not have this information:
reply loginctl show-user $USER 2>/dev/null
userdbctl user $USER --json=pretty 2>/dev/null | grep -i birth
homectl inspect $USER | grep -i birth
sudo homectl update $USER --birthday=""
If the browser gets passive / aggressive updates if they mimic Microsoft and refuses to run if there is no age set then script a random age or age range on each login so that it is not used for tracking.
They can do that with or without an existing law.
replyWithout signaling nothing would happen. There's always signaling.